Explaining that Magical Period between 1986 and 1996 where some of the best DOS games were released
One thing everyone talks about in the "retro PC" circles, is the "Golden Age of DOS Gaming" - a magical period of massive technological improvement in IBM PC Compatible computer games. The period starts around 1986 and ends around 1996, starting roughly around the time of the TAndy 1000 series taking off, AGI Sierra Graphical Adventures, Tetris, and elaborate flight sims. It ended as Windows 95 took a stranglehold on the desktop worldwide, and basically replaced DOS as the preferred operating system for game developers.
PC Games Before This Period
Prior to this period, the IBM Personal COmputer, and it's clones, were seen as BUSINESS machines. That's what they were designed, built, and intended for. Actually, that was pretty much any *serious* computer from a *serious* company like IBM (Such as Hewlett Packard, Digital Equipment Corp, and others). These were not "Toys" they were "Business Machines" - meant to crunch numbers, create graphs and charts, and perform correspondance of the professional variety. And adults back in the eighties, if they wanted to play games, they played pinochle, pachinco, or joined a Wesson Oil Party covered up as "date night". The games? Oh, that's for those meddling kids! THey already have an Atari - that sucked up $200 - so I'm not spending $2000 so my kid can play (a very janky and poorly rendered) clone of Defender when I need to do my Taxes! (But they are for Daddy to mess around on while the boss is away, hell, half of em' look like work anyway being in 80x25 column text mode, and he don't know that newfangled computer crap - so he'll never know I'm playing Colassal Cave instead of writing a letter to Debbie in ACcounting for those TPS Reports).

Old DOS Games, let's face it, they were ugly, simple, clunky, a lot of them REQUIRED a 4.77 MHz 8088 PC to run properly, and even then, they were glacially slow if the coder was not using x86 assembly/machine language. Yeah, later on you got graphics - very limited 4-color CGA Graphics - but they were graphics anyway. There were some exceptions but a lot of those were just later ports of earlier games for the Apple II, Commodore 64, and Atari 800 (more game-oriented machines, I'm looking at you Ultima). But for the most part, there were some diamongs in the rough (Microsoft Adventure, B.C.'s Quest for Tires), but nothing to write home about.

Basically put, they were simple little time wasters, mostly based on arcade games of the day, limited to 4 colors in 320x200 pixel CGA, using the simple monotone PRogrammable Interrupt TImer based beeper speaker to make sound and music, of which you could not control the volume of, and sometimes, could not turn off.
What Ushered in this awesome era
The roots of the Age start with IBM's biggest failure - the IBM 4860 PC Jr - a crippled IBM PC that could use Game Catridges, had no DMA, no 8087 support, and was designed as a "home computer" with a barely capable Infared Chiclet keyboard (which they later redesigned and replaced). The PC Jr. was not a BAD machine, it was just not that great to be paying IBM level prices for. But it technically IS the FIRST Multimedia PC. Why do I say this....well....

The IBM PC Jr. featured new enhanced graphics in the form of a "CGA Superset" known as "PC Jr. Video" - or later on "TGA" (TAndy Graphics Adapter), and a new 3-voice audio system consisting of a popualr sound chip found in arcade games combined with the original PIT based beeper. While the PC Jr was a failure, another company, Tandy, decided to take over the features on their new "1000" computer. The Tandy 1000 was released in 1984, but due to the failure of IBM's flagship product, the Tandy 1000 focused on it's PC Compatibility, and managed to become one of the most popular IBM COmpatible computers of the 1980's.

During the PC JR.s development, fledgling California Game company, Sierra On-Line, owned by Ken and Roberta Williams, was brought on to design a new game for the new PC Jr. to help aid sales. They wanted something that would wow the audiences and show off the new PC's capabilities in sound and graphics. That product would be King's Quest - which was really the first major Graphical ADventure game Release.

King's Quest was basically a sandbox where the player could autonomously roam around and solve the puzzles in basically any order they wished for the most part. It was kind of like the precursor to today's first person RPG games. Basically, you were cast in the role of "Sir. Grahame" - the next up to the throne of hte kingdom, and you had to go on a quest to rid the kingdom of various evils and prove yourself worthy to the throne, mostly through a series of various puzzles - basically - the fist full on Graphical Adventure game. While Ken and Roberta did similiar with games like Mystery House prior - this game was a step above that.

While King's Quest was influential, other genres of DOS game started to grow and get better too. EGA Graphics became a thing around 1984-1985ish, which now allowed standard, regular PCs to have full 16-color graphics like the Tandy, further enhancing the sound. Creative Labs created their first product, the Game Blaster, which gave similar sound to the PC Jr. and Tandy 1000 (same sound chip I believe), and later, in 1987, Adlib would release the first of their famous Yamaha YMF-262 OPL FM Synthesizer chip based "Adlib" cards. Setting the stage for what is to come.

By 1987, when Adlib and VGA came out - we already had many classic series in the works. Sierra had King's Quest, Space Quest, Leisure Suit Larry, and was now importing games from Japan (Thexder, Silpheed, and Zeliard to name a few). LucasFilm now had their own games division with Ron Gilbert creating the engine that would drive almost all of the games that would become cult classics thereafter - SCUMM - or Script Creation Utility for Maniac Mansion, which included to that point Maniac Mansion, Zakk McKraken and the Alien Mindbenders, and Indiana Jones was in development for release soon.

This set the stage for what was to come. To add to it, the computer industry was changing. IBM was no longer top dog because of missteps to try and close the PC market with the IBM PS/2 series, Compaq had a change of management and was shifting to be more consumer focused, Michael Dell rebranded his company from "PC's Limited" to "Dell" - now the biggest company in the world, Gateway 2000 was taking off, some goons bought the Packard Bell name and started selling budget PCs under that name, and Tandy was finishing up with their 1000 series with 286 and even a 386 powered version. The PC was coming of age. And brewing in the background was a joint operation between Microsoft and IBM for the "Next Generation O/S" - OS/2 - which would later split off into two - OS/2, and Windows NT (basically).

I would set the peak of the Golden age of DOS Gaming at 1989-1993 - because a grand lot of the hugest releases would come out. at that time (as we will soon see as we look at these influential games more). In that time period we got The Secret of Monkey Island, Commander Keen, Wolfenstein 3D, Sim City, Wing Commander, Loom, The Lost Vikings, Lemmings, Scorched Earth and Tank Wars - I mean, just look up the majority of the most referenced DOS games - most of these came out during the 1989-1993 period.

I'd say the last period of this would be 1993 which would be now when we had Doom, which was really the last tremendously popular DOS game, so much so, that it made the transfer over to Windows via Direct X just a couple years later (Doom95). The side effects of this is that we would end up with FPS leeching it's way into every genre as real 3D (and not RayTracing/RayCasting - which is what Doom and Wolfenstein 3D Used), to a point that the effects of Doom's impact can still be seen today 31+ years later in modern game design. On top of that, it's been sort of a trope-ish goal for people to get Doom running on just about anything with a Microprocessor from Smart Fridges to graphing Calculators.

What ultimatley killed DOS gaming was the proliferation of Windows as the default desktop on PCs, and 3D Gaming, plus the march of technology "forward" which meant more memory was needed, and the old, inefficient techniques DOS used to map memory and put things in memory, was just out of the question when you start talking games that run higher than 1024x768p at 32-bit color, with 3D rendered graphics.
The Classics - A Quick Compendium to the CLASSIC DOS Games Everyone Should Know
King's Quest
1984 Sierra On-Line
Roberta Williams
Originally designed to highlight the glory of the brand new IBM 4860 PC Junior upon release in 1984, King's Quest really showed what PCs could really do with gaming, and paved the way for the future and the Golden Age. What we had was a 16-color enhanced CGA DOS Game with 3-voice audio, and a full open world to explore. While hard as nails, a bit difficult because it was still early enough to rely on a thickish book of documentation to understand the story and gameplay, and more keyboard commands than most people were used to for leisure back then, King's Quest really paved the way for the future of the IBM PC from that point forward. That said, it really hit it's stride with the 1987 updated re-release that improved the Adventure Game Interpreter (AGI) Game engine's handling of graphics and text boxes, and gave a more elegant, polished presentation compared to the 1984 IBM-branded original.
Ultima IV: Quest of the Avatar
1984 Origin Systems
Richard Garriott
While it was seriously tempting to put the entire Ultima series on here, I had to restrain myself, because Ultima 0-III (yes I count Akalabeth as Ultima 0 here), were laregely Apple II creations, whereas Ultima IV was more PC-focused. Also, it was highly influential because it was the first case in gaming history, where the quest did not involve some major bad guy. Ultima IV is a SPRITIUAL QUEST of sorts, a sacred journey, where Virtue is the focus. Sure, there's monsters, there's fights, but handling everything is far more different than in any other game, even within the Ultima series. It is believed this game was a response to people acting like total bastards in Richard Garriot's earlier games (which sometimes you had to do to win), as well as the Christian Coalition's B.S. about these "Role Playing GameS" being "Satanic". It also seems to be where Brittania/Sosaria got a polished, focused canon that lead to more releases in the future.
Police Quest
1986 Sierra On-Line
Jim Walls
Police Quest was created by designer and ex-cop Jim Walls as a realistic simulation of life as a member of Law Enforcement. What made this game impressive is just how stuck to protocol it was. I mean, literally, you had to make sure to follow every Police protocol to the letter or you'd either die, get fired, or worse. This included things as mundane as taking showers, inspecting your squad car, making sure to pick up a walkie talkie (Responder), reading miranda rights and performing arrest proceedures in proper order, working with the fucked up court system (which was far less fucked up in America and Police Quest in 1986). It was a concept really ahead of it's time as signified by the frustrating level of minutiae required to complete the game, not to mention rather difficult driving sequences (especially to those of us not used to using a numeric keypad).
Leisure Suit Larry in the Land of the Lounge Lizards
1986 Sierra
Al Lowe
Leisure Suit Larry was likely the first case of a re-imagined remake in computer gaming history. The entire game is based off an earlier one Sierra released called "Softp*** Adventure". Comedian/Musician/Designer Al Lowe basically took the plot to that game and refined it into a hilarious graphical adventure on par with some hollywood movies of the time. The whole game revolves around a 40 year old, uh...."inexperienced" man kicked out of his mom's house on a quest to find a woman, and well, you know the rest. So was the start of Larry Laffer who would end up with 5 sequels in his original run (not including Leisure Suit Larry 4: The Case of the Missing Floppies).
Space Quest: The Sarien Encounter
1986 Sierra
Those Guys from Andromeda
Space Quest was a SciFi Comedy graphical adventure created by "Two Guys from Andromeda" - a pair of designers at Sierra who liked to dress up as aliens for all their Public Relations apparently. The game is sort of a rip of Star Trek, Star Wars, 2001: A Space Odyssey, and maybe Space Balls, but does it better than that last one. You play as Rodger Wilco, space janitor, who likes sleeping in the supply closet a lot apparently. You wake up from a nap to find that your entire ship has been ransacked by aliens and have to escape before they find and kill you. This leads Rodger Wilco on a wild adventure on various planets and in outer space. Pretty wild game.
Maniac Mansion
1987 LucasFilm Games
Ron Gilbert
In 1982, LucasFilm - yes the same company that created Star Wars, decided to open up their own games division at Skywalker Ranch. Around 1985 or so, they hired on a developer/designer named Ron Gilbert, who created a game engine and scripting language known as SCUMM to create what would be one of the most influential games for DOS since King's Quest - Maniac Mansion. In Maniac Mansion, you get to pick from a group of kids from the local high school to save Dave's girlfriend Sandy from the Edison Family - a family of a mom, dad, and a kid, corrupted by an evil Comet, who live in a creepy mansion on the outskirts of town. This would mark the start of one of the most successful franchises of the late 80's/early 1990's, and was really one of the games popular enough to signify (with the help of a King's Quest reprint using an updated AGI interpreter) that would kick off the "golden age of DOS Gaming".
Leisure Suit Larry: Larry Goes Looking for Love (In Several Wrong Places)
1987 Sierra
Al Lowe
In 1987, on the heels of the success of Al Lowes Leisure Suit Larry in the Land of the Lounge Lizards, Al Lowe got to leverage the new "Sierra Creative Interpreter" or SCI engine for this game, which takes us on a new story with Larry Laffer after the events of the first game, where Eve kicks him out of her house, and Larry wins a game show for a trip to an island for a vacation. The improved visuals and added support for Adlib Sound really brought a lot of the Sierra games using this interpreter into the public eye a lot more than previous.
Ultima V: Warriors of Destiny
1988 Origin Systems
Richard Garriott
After Ultima IV, Richard and his team focused on storytelling, in a Frank-Zappa-Esque twist of events. Ultima V: Warriors of Destiny tells a story about legislating morality - the same kind of things musicians like Dee Snider, John Denver, and most especially Frank Zappa were already commenting on on the news to the US Government regarding "Decency Laws". In Ultima V, Lord British has gone on a dungeon expedition and is presumed lost, and his appointed "acting King" for the time, Lord Blackthorne, has started forcibly enforcing the eight virtues while himself being corrupted by three evil beings known as the "Shadowlords". The game took what was started in Ultima IV and started bringing interactivity to an impressive level, being able to steal crops, find secret passages, play pianos, sleep in beds, and fire cannons - foreshadowing what was to come in Ulitma in 1990.
Tank Wars
1988 Kenneth B. Morse
1989 LucasFilm Games
The Secret of Monkey Island
1989 Lucasfilm Games
Ron Gilbert
This cult classic was the first Graphical Adventure to utilize the rules set out in Ron Gilbert's Why Adventure Games Suck published in The Journal of Computer Game Design in 1989. Monkey Island followed these principals making for one of the best games (and series) in the genre. In Monkey Island, we follow Guybrush Threepwood, a wannabe pirate, through his trials and tribulations to become a pirate, and persue the governor of Melee island, Elaine Marley with amorous ambitions. People today way over-estimate the popularity of PC games and cite this one as some kind of tremendous release, but the truth was almost every game on this page was a niche thing at the time because PC gaming was not quite as popular until Windows 95 came out in 1995. But out of the lot, this is one of the biggest classics of the genre.
Street Rod
1989 California Dreamin'
Sim City
1989 Maxis
Will Wright
Wolfenstein 3D
1989 I.D. Software
Sid Meir's Civilization
Street Rod II
1990 California Dreamin'
Ultima VI: The False Prophet
1990 Origin Systems
Richard Garriot
Ultima VII: The Black Gate
1991 Origin Systems
Richard Garriot
1992 I.D. Software
Ultima VII Part 2: The Black Gate
1992 Origin Systems
Richard Garriot
Freddy Pharkas Frontier Pharmacist
1993 Sierra
Al Lowe & Josh Mandel
Sim City 2000
1994 Maxis
Will Wright
Duke Nukem 3D
1996 Apogee